In order to avoid the problem of motor shaft breakage, motor manufacturers will conduct necessary control on the material quality, processing technology, and shaft design of the motor shaft. However, for motor users, they should communicate with the motor manufacturer for specific installation.

If the same problem occurs on the same product, or the same problem only occurs on the same customer, it is necessary for us to fully analyze this type of problem, and the supply and demand parties can solve the substantive problems through in-depth communication. How to choose a motor?

When choosing a motor as a power machine, the main thing is to determine the type and specification of the motor. The type of motor to be selected needs to consider the load characteristics of the working machine, the production process requirements, the operating environment, and the power supply conditions of the power grid. The main principle for determining the motor specification is to verify the heating, starting torque, and overload torque of the motor according to the production process and load conditions. If the production process does not require speed adjustment, the AC motor should be considered first: if the load is stable, a general squirrel cage asynchronous motor can be selected; if the machine needs to start under heavy load, a squirrel cage asynchronous motor or a winding asynchronous motor with high starting torque can be selected. Many working machines require speed adjustment, and some only need the motor to adjust the speed at a few levels, such as machine tools. In this case, a multi-speed AC asynchronous motor can be used. If there are higher requirements for speed adjustment, a DC separately excited motor should be used.

Motor starting methods

Motors are divided into two types: direct starting and reduced voltage starting. For squirrel cage asynchronous motors, direct starting should be preferred. However, when starting directly, the starting current usually reaches 4 to 7 times the rated current, while the starting torque is only 0.8 to 1.5 times the rated torque. Due to the large starting current, it is necessary to consider whether the grid capacity allows it.

There are three methods for reduced voltage starting: ●Resistor or reactor voltage reduction: When starting, connect a resistor or reactor in series in the stator winding, and short-circuit it after starting. When this method is used to reduce the starting current to 1/K times, the starting torque is reduced to 1/K2 times. ●Star-delta voltage reduction: When starting, temporarily connect the stator winding in star, and then change the stator winding to delta after starting. This method is only applicable to motors with delta stator windings during normal operation. It can reduce the grid current to 1/3 of direct starting, and the starting torque is also reduced to 1/3 accordingly. ●Autotransformer voltage reduction: When starting, the motor is powered by an autotransformer, so that the motor voltage is reduced to 1/K of the rated voltage. After starting, the autotransformer is removed and the motor is directly connected to the grid. When starting with this method, the grid current and torque will be reduced to 1/K2 of direct starting.

Reduced voltage starting is only suitable for starting with a lighter load. If you want to limit the starting current and have a larger starting torque, you must use a wound asynchronous motor, connect a starting resistor in series in the rotor winding circuit, and cut off the resistor step by step during the starting process. In order to simplify the starting equipment and improve the starting characteristics, frequency-sensitive resistors are often used instead of starting resistors. For DC motors, direct starting is generally not allowed except for small-capacity ones. In order to limit the current, a starting resistor must be connected in the armature circuit.

Electro motor, low voltage alternator, asynchronous electric motor